From reading lots of the rumours around Alfa, here's my summary.
There are five models that have been mentioned as in development. All, bar one, are bigger than Giulietta:
1. Compact SUV (X3 or Q3 sized, based on 2014 Jeep Cherokee)
2. Ghibli-based 169 replacement (5-Series, E-Class, A6 size)
3. Giulia (3-Series, C-Class, A4 size)
4. Giulia Sportwagon
5. New Spider, co-developed with Mazda MX-5
(4C is already being delivered, so that's not a "future" model).
The only public dates are from the investor presentations, which just said:
Early 2014: two models
2015: Spider plus two other models
No presentation has ever said which car was to come when, but it was taken to mean 2014 for both Giulia versions, and 2015 for SUV, 169, Spider. Spider is fixed at 2015, because that's Mazda's announced date too. (the dealer who confirmed the details of the Giulietta facelift way back in January also said that Giulia would be a 2014 launch, but things could have changed since then)
Since then, there is a persistent rumour that Giulia and the 169 have swapped places, and that the bigger car will launch in 2014, but the Giulia sisters will be delayed for another year and launch in 2015.
In terms of drivetrains, Giulia was originally planned as Front-wheel drive with 4x4 as option (based on a further-extended version of the architecture used for the Dodge Dart), the SUV was Front/4x4 on the same architecture (already used in the 2014 Jeep Cherokee), and Spider and Ghibli/169 will be both Rear-wheel drive.
However, rumours coming from inside Chrysler say that a compact Rear-wheel drive design has been developed for use by both Alfa Romeo and a future Dodge Avenger (a car that itself had been marked to be discontinued in 2014 and not replaced). This design would be used for the Alfa Giulia, which, if the rumour was true, would make Giulia Alfa's first RWD saloon since the 1980s (unless the 169/Ghibli gets there first)
Such a development would mean that all Alfas above the Giulietta would be RWD, which is something that Marchionne has stated would be his "ideal situation" for as long as he's been running FIAT.
New engines were to be developed with technical assistance from Ferrari. Most likely this would mean a new V6 petrol, above the 1750. The new Maserati V6 will most likely not see the inside of an Alfa: it's almost entirely hand made, and would be too expensive for the volume that Alfa would need (the V6 would be the entry engine in the USA).